pooch, if you hang it vertically that you need spring tension opposite the ball to keep the barrel against the ball as you are reading it. The one advantage of doing it vertically is that you can read from bottom rib to top rib easily by just rotating the barrel. The hard part is you need someone to write the numbers down or else you have to take the barrels off the gage and write down the numbers.
Again this is my opinion, using the Manson, Clymer gage in the horizontal position and holding the barrels down and sliding the gage into them, is that you can only take a partial reading and then have to move the barrels maybe a few more times to get complete readings from bottom rib to top rib. There is only so much you can move the gage before the weight of the bar is not making good contact with the ball bearing on the barrel.
The Galazan gage is a lot easier to use. The hardest thing about making it is milling the area for the spring. It is a tapered slot that when the tapered brass piece is in place and compressed, it is the same size as the shaft (5/8") plus the ball bearing that is drilled into it. I believe the ball bearing I used was 3/16", so less than 3/32" is sticking out.
